Prior electronic compasses having a plurality of sense windings are known. These compasses are typically referred to as flux gate compasses. Such compasses generally have two sense windings oriented in nominally orthogonal directions with respect to one another. The output voltage signals produced by these windings are then utilized to provide an indication of compass heading or direction wherein the terms "heading" and "direction" are used interchangeably herein. Theoretically, if the windings were perfectly orthogonally aligned, and if there were no disturbances to the earth's magnetic field, the outputs of the sense windings would, when plotted against each other on an x y coordinate system, result in a circle locus. However, due to various magnetic effects, the actual plot of the sense output winding outputs results in an elliptical path.
Some prior electronic compasses have recognized that an elliptical locus is provided for the outputs of the sense windings due to magnetic field disturbances. Some prior compasses have attempted to correct the compass headings provided by such compasses by calculating the ellipse center coordinates and the ellipse major and minor axis radii and using these calculated parameters to calibrate the compass. However, such systems assume that the sense windings are exactly orthogonally aligned and that therefore no additional compensation or correction is required. These prior compass systems just compensate in accordance with the calculated ellipse center coordinates and the ellipse radii since generally great care is put into manufacturing electronic compasses having windings which are substantially orthogonal to one another. However, there can be appreciable errors in the compass heading provided by an electronic compass due to any slight non-orthogonal alignment of the sense windings. Typically this type of error is not compensated for or is not sufficiently compensated for. The result is that these compasses are not suitable for providing very accurate navigation headings. This is especially significant when the compass is used for vehicle navigation and the vehicle is not traveling on predetermined roads, since then conventional map matching can't be used to correct the compass heading.
It is possible to calibrate a compass by creating an extensive calibrated look-up table by orienting the compass in a very large number of known directions and storing the outputs of the sense windings provided for each such known direction. However, such a technique is time consuming and requires orienting the compass in a very large number of exactly known directions and this is not practical. If only a few known directions are used to create such a table, a less accurate compass is provided which is susceptible to winding alignment errors.